Telemeter having image flux separator with opaque area at an acute angle with the optical axis

ABSTRACT

The invention provides a high sensitivity in a telemeter of the type including a convergent optical receiving system reflecting the rays from the object the range of which is to be ascertained and two different photocells the exposure of which to said rays varies in opposite directions in accordance with the location of the point of convergence of said rays and to this end there is provided an element separating the rays impinging on the group of photocells and extending along a straight line passing through a predetermined point of convergence between two ranges of points of convergence for which the photocells are selectively predominant.

' United States Patent Inventors Appl. No.

Filed Patented Assignee Priority TELEMETER HAVING IMAGE FLUX SEPARATORWITH OPAQUE AREA AT AN ACUTE ANGLE [50] Field of Search 250/208, 209,210, 220, 237

[56] References Cited UNITED STATES PATENTS 3,320,850 5/1967 Oliver250/220 Primary Examiner.lames W. Lawrence Assistant Examiner-T. N.Grigsby Attorneys-Emory L. Grofi and Emory L. Groff, Jr.

ABSTRACT: The invention provides a high sensitivity in a telemeter ofthe type including a convergent optical receiving system reflecting therays from the object the range of which is to be ascertained and twodifferent photocells the exposure of which to said rays varies inopposite directions in accordance with the location of the point ofconvergence of said rays and to this end there is provided an elementseparating the rays impinging on the group of photocells and extendingalong a straight line passing through a predetermined point ofconvergence between two ranges of points of convergence for which thephotocells are selectively predominant.

WITH THE OI'IICAL AXIS 10 Claims, 6 Drawing Figs.

US. Cl 250/220, 250/237 Int. Cl H0lj 3/14, HOlj 5/16, HOlj 39/12PATENTED SEP 7|97| 3.803.800

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ATTORNEY TELEMETER HAVING IMAGE FLUX SEPARATOR WITH OPAQUE AREA AT ANACUTE ANGLE WITH THE OPTICAL AXIS The present invention relates to atelemeter chiefly intendedfor photographic purposes, of the typeincluding a convergent optical receivingsystem and at least twophotoelectric elements exposed to the light rays received by the opticalsystem and produced by the object the range of which is to beascertained, said photoelectric elements being located in a manner suchthat their exposure varies in a reverse ratio with reference to eachother in accordance with the distance at which said rays converge.

In order to obtain a proper sensitivity for the telemeter it isnecessary to measure with a high accuracy the distance at which the rayscollected by the receiving optical system converge. The US. Pat.application Ser. NO. 686,554 relates to a telemeter of said type whichallows an excellent accuracy of measurement, but which includesintricate and expensive means defining the distanceof convergence.

The present invention has for its object to solve simply, economicallyand efficiently the problem of the measurement of the distance ofconvergence in such a telemeter. This result is achieved by means of atleast one separating element which is at least partly opaque and has anedge arranged so as to form a separating line between the loci ofconvergence of said rays for two distances of convergence which are nearone another, said separating element being substantially flat andforming an angle less than 90 with the optical axis of the receivingsystem.

The accompanying drawings illustrate diagrammatically and by way ofexample various embodiments of said improved telemeter. In saiddrawings:

FIG. 1 is a partial view of a first embodiment of the telemeter.

FIG. 2 shows on a larger scale a detail of FIG. 1.

FIG. 3 illustrates a detail of a modification including a ray deflectingelement.

FIG. 4 illustrates a second embodiment showing uniform reflectingblades.

FIG. 5 shows another embodiment without any reflecting blades.

FIG 6 illustrates another embodiment without any reflecting blades butwith a ray deflecting element.

FlG. 1 illustrates the principle of the optical operation of a telemeterincluding a lamp 1, a reflector 2 projecting the luminous rays producedby the lamp 1 towards the object the distance of which is to beascertained, a convergent optical receiving system 3 including the twoterminal fractions of a diametrical strip forming part of a concavemirror, said receiving system being adapted to collect the rays issuingfrom the object. A blade 4 provided with reflecting surfaces constitutesa flat mirror extending along the optical axis 7 and two photoelectricelements 5 and 6 provided with light guiding means, and 16 respectivelyare located to either side of said opticalaxis.

The luminous rays produced by the lamp 1 are reflected by the reflector2 and directed as a beam of rays parallel with the optical axis 7 of thereflector 2 towards the object of which it is desired to measure thedistance. A fraction of the rays reflected by said object impinges ontothe convergent optical system 3, the optical axis of which registerswith that of the reflector 2, said fraction reaching the oppositereflecting sides of the blade 4 forming a separating element anddirecting said rays towards the photocells 5 and 6.

FIG. 2 illustrates a detail of the blade 4 which the reflecting areasinclude an aluminum coated part 9 on one surface of the blade 4, theother area 8 of said surface being black. The opposite surface of saidblade 4 is provided with a reflecting area 11 registering with the blackarea 8 of the first-mentioned surface and a black area 10 in registrywith the reflecting area 9 of said first-mentioned surface. Eachreflecting area 9 or 11 is separated from the cooperating area, 10 or 8respectively, by a rectilinear edge, 9' or 11' respectively, forming aseparating line between the loci of convergence of said rays for twoadjacent ranges of convergence.

When the object considered moves, .for instance when it moves away fromthe measuring apparatus, the point of convergence of the rays movestowards the right-hand side of FlG. 2. The luminous beam reflected bythe fraction of the concave mirror 3 extending underneath the opticalaxis impinges gradually more on the black absorbent area 8 while theluminous bema reflected by the opposite fraction of the mirror impingesgradually more onto the reflecting area 11.

There is thus obtained a reduction in the illumination of the photocell5 and an increase in that of the photocell 6. Obviously, if the point ofconvergence of the collected rays moves towards the left hand side ofFIG. 2 over the blade 4 the conditions of illumination of the elements 5and 6 are reversed.

The photocells 5 and 6 which are preferably photoconductive are insertedin an electric circuit which is not illustrated, for instance of thetype disclosed in the US. Pat. application referred to hereinabove Ser.No. 686,554 so as to supply at least one electric signal controlling anauxiliary mechanism adapted to shift the blade 4 in its plane until thecooperating rectilinear edges of the reflecting areas 9 and 11 registerwith the point of convergence of the rays reflected by the concavemirror 3.

FIG. 3 illustrates a modification of the blade 4 which includes a tworeflecting areas 12 and 13 located substantially in a plane passingthrough the optical axis 7 or very near said plane and separated by atransparent area 14. The limit between the transparent area 14 and eachreflecting surface 12 or 13 is constituted by a rectilinear edge 12' or13 respectively. The convergent optical system is designed in a mannersuch that the foci of its two fractions are spaced along the opticalaxis 7 by a distance equal to that separating the two rectilinear lines12' and 13'. Said spacing is obtained by a transparent block 17 insertedin the path of the convergent beam passing off one fraction of thesystem 3. Said block 17 may be made of glass or of plastic material.

When the convergent rays move towards the right-hand side of the blade 4to either side of the latter, in direct relationship for instance withthe movement of the object away from the blade 4, said rays issuing fromthe lower fraction of the optical system and reaching the area 13 aredeflected to an increasing extent towards the photocell 6 while the raysof the beam from the upper fraction of the optical system move graduallyaway from the reflecting area 12 so as to impinge onto the transparentarea 14 and to reach a gradually lesser extent the photocell 6 whereby adifference in illumination between the photocells 5 and 6 is obtained.

In the embodiment illustrated in FIG. 4, the telemeter includes twomirrors l8 and 19 arranged in parallelism to either side of the opticalaxis 7 of the optical receiving system 3 which is constituted by adiametrical strip cut out of a concave mirror. Each of said mirror 18,19 reflects the rays received from the concave mirror 3 towards a groupof two photocells 20, 21 and 22, 23 respectively, The two photocells ofeach group are associated with a blade 24 or 25 respectively, the planeof which is set so as to be substantially parallel with the generaldirection of the rays reflected towards the group of photocellsconsidered. Both surfaces of said blades form reflecting areas and therectilinear edge of each blade, which is nearest the optical system,lies in proximity with the point of convergence of said rays. Thus, whenthe point of convergence to one side of the optical axis registers withthe corresponding rectilinear edge, the two photocells of the associatedgroup of photocells are illuminated equally.

When the distance at which the rays converge increases, the point ofconvergence of the rays moves outwardly with reference to therectilinear edge so that the photocells 21 and 23 receive more lightthan the photocells 20 and 22, If, in contradiction, the distance ofconvergence decreases, the conditions of illumination of the photocellswould be reversed.

It should be noted that the blades 24 and 25 forming separating elementsare not necessarily of a reflecting type. As a matter of fact, the partsof said blades adjacent the rectilinear edges cut off the rays whichwould otherwise impinge on one of the photocells as soon as the point ofconvergence of the rays no longer registers exactly with saidrectilinear edge. However, when the surfaces of the said blades are of areflecting character, the rays which have been cut off and no longerreach one photocell are reflected towards the other photocell whichreinforces the effect due to the lack of balance between theilluminations provided for the two photocells. This still furtherincreases the sensitivity of the arrangement.

FIG. 5 illustrates another embodiment similar to that of FIG. 4 exceptfor the fact that the two plane mirrors 18 and 19 are eliminated. Inorder to produce two separate points of convergence for the raysreflected by the two fractions 3' and 3" of the reflecting system, thelatter includes two independent portions forming parts of a concavemirror, each portion being provided with its own optical axis 7 or 7".It is thus possible to make the rectilinear edge of the separating areas24 and 25 of each group of two photocells lie on the correspondingoptical axes 7 and 7' respectively.

The operation of said telemeter is exactly similar to that disclosedwith reference to FIG. 4 when the point of convergence of the raysreflected by the optical reflecting system is shifted along the opticalaxes.

FIG. 6 illustrates a modification wherein the two groups of photocells20 and 21, and 22 and 23 are located along the optical axis 7 of anoptical system 3 constituted by a diametrical strip cut out of a concavemirror. The two active portions 3 and 3 of the reflecting system reflectrays towards the corresponding groups of two photocells and, in order tomake each of said groups sensitive to the rays issuing out of only oneof said active reflecting portions, the distance of convergence of therays from the portion 3' is increased optically by a transparent block17 with parallel surfaces made of glass or plastic material. Thus thetwo groups of photocells may be located one behind the other along thesame optical axis, the block 17 being inserted across the path of therays impinging onto the group of photocells furthest away from theconcave mirror.

We claim:

1. In a telemeter for measuring the distance of an object, particularlyfor use in photography, comprising projector means for directing a lightbeam to an object whose distance is to be measured, a convergent opticalreceiving system capable of forming an image of the portion of theobject lighted by the light beam, with the impinge formed by saidconvergent optical system being shifted parallel to itself along theoptical axis of said optical receiving system depending upon thedistance of the object from said optical receiving system, a detectordevice comprising at least one separator element for separating theluminous flux forming the image into two separate beams with theproportion of the luminous fluxes forming the two means being dependenton the position of said image with respect to that of said separatorelement, and at least one pair of photocells measuring and comparing theintensity of the luminous fluxes of the two beams, the improvementwherein said separator element comprises at least one opaque areaforming an angle of less than 90 with the axis of the optical convergentsystem and having an edge located at least neat the point of convergenceof the image.

2. In a telemeter as claimed in claim 1, wherein each separator elementcomprises a blade to either side of which the photocells of thecorresponding pair of photocells are set, said blade extending insubstantial parallelism with the reflected rays impinging on saidphotocells.

3. In a telemeter as claimed in claim 1, the further improvement whereinthe convergent optical receiving system includes two separate reflectingfractions adapted to reflect separate portions of the light issuing fromthe object, the optical axes of said fractions extending in parallelismwith a predetermined direction.

predetermined direction, each separator element comprising a blade toeither side of which the photocells of the correspond ing pair ofphotocells are set, said blade extending in substantial parallelism withthe reflected rays impinging on said photocells, and reflected by thecorresponding fraction of the optical system.

5. In a telemeter as claimed in claim 1, the further improvement whereinthe convergent optical receiving system includes the terminal reflectingfractions of a diametrical strip cut out geometrically of a concavemirror, said telemeter including furthermore two parallel plane mirrorslocated to either side of the optical axis of the concave mirror andadapted to reflect the rays of the convergent beam reflected by thecorresponding terminal reflecting fractions onto the corresponding pairof photocells, each separator element comprising a blade to either sideof which the photocells of the corresponding pair of photocells are set,said blade extending in substantially parallelism with the reflectedrays impinging on said photocells.

6. In a telemeter as claimed in claim 1, the further improvement whereinthe convergent optical receiving system includes two marginal fractionsformed in concave mirrors the axes of which are parallel and spaced withreference to each other.

7. In a telemeter as claimed in claim 1, the further improvement whereinthe convergent optical receiving system includes terminal reflectingfractions of a diametrical strip cut out geometrically of a concavemirror, said telemeter including two pairs of photocells locatedadjacent spaced points of the axis of said concave mirror and of whichone receives the rays reflected by one reflecting fraction and atransparent parallel sided block inserted in the path of the raysreflected by each other reflecting fraction to make them impinge on theother spaced point.

8. In a telemeter as claimed in claim 1, the further improvement whereinthe convergent optical receiving system includes two separate reflectingfractions adapted to reflect separate portions of the light issuing fromthe object, the optical axes of said fractions extending in parallelismwith a predetermined direction and wherein the separating elementincludes reflecting areas extending along the axes of the separatereflecting fractions and facing the corresponding fraction to reflectthe rays from the latter onto the corresponding photocells, the outeredges of each reflecting area extending in a plane passing between thereflecting fractions along rectilinear lines perpendicular to thedirection of the axes.

9. In a telemeter as claimed in claim 1, the further improvement whereinthe convergent optical receiving system includes two separate reflectingfractions adapted to reflect separate portions of the light issuing fromthe object, the optical axis of said fractions extending in parallelismwith a predetermined direction and wherein the separating elementincludes reflecting areas extending along the axes of the separatereflecting fractions and facing the corresponding fraction to reflectthe rays from the latter onto the corresponding photocell, the outeredges of each reflecting area extending in a plane passing between thereflecting fractions along rectilinear lines perpendicular to thedirection of the axes, the side of each reflecting area facing away fromthe corresponding reflecting area being black.

10. In a telemeter as claimed in claim 1, the further improvementwherein the convergent optical receiving system includes two separatereflecting fractions having different foci, adapted to reflect separateportions of the light issuing from the object, the optical axes of saidfractions extending in parallelism with a predetermined direction, andwherein the separating elements include two coplanar reflecting areasrectilinear lines perpendicular to the direction of the axes of thereflecting fractions and spaced by an amount equal to the spacing of thefoci of said fractions,

1. In a telemeter for measuring the distance of an object, particularlyfor use in photography, comprising projector means for directing a lightBeam to an object whose distance is to be measured, a convergent opticalreceiving system capable of forming an image of the portion of theobject lighted by the light beam, with the impinge formed by saidconvergent optical system being shifted parallel to itself along theoptical axis of said optical receiving system depending upon thedistance of the object from said optical receiving system, a detectordevice comprising at least one separator element for separating theluminous flux forming the image into two separate beams with theproportion of the luminous fluxes forming the two means being dependenton the position of said image with respect to that of said separatorelement, and at least one pair of photocells measuring and comparing theintensity of the luminous fluxes of the two beams, the improvementwherein said separator element comprises at least one opaque areaforming an angle of less than 90* with the axis of the opticalconvergent system and having an edge located at least neat the point ofconvergence of the image.
 2. In a telemeter as claimed in claim 1,wherein each separator element comprises a blade to either side of whichthe photocells of the corresponding pair of photocells are set, saidblade extending in substantial parallelism with the reflected raysimpinging on said photocells.
 3. In a telemeter as claimed in claim 1,the further improvement wherein the convergent optical receiving systemincludes two separate reflecting fractions adapted to reflect separateportions of the light issuing from the object, the optical axes of saidfractions extending in parallelism with a predetermined direction.
 4. Ina telemeter as claimed in claim 1, the further improvement wherein theconvergent optical receiving system includes two separate reflectingfractions adapted to reflect separate portions of the light issuing fromthe object, the optical axes of said fractions extending in parallelismwith a predetermined direction, each separator element comprising ablade to either side of which the photocells of the corresponding pairof photocells are set, said blade extending in substantial parallelismwith the reflected rays impinging on said photocells, and reflected bythe corresponding fraction of the optical system.
 5. In a telemeter asclaimed in claim 1, the further improvement wherein the convergentoptical receiving system includes the terminal reflecting fractions of adiametrical strip cut out geometrically of a concave mirror, saidtelemeter including furthermore two parallel plane mirrors located toeither side of the optical axis of the concave mirror and adapted toreflect the rays of the convergent beam reflected by the correspondingterminal reflecting fractions onto the corresponding pair of photocells,each separator element comprising a blade to either side of which thephotocells of the corresponding pair of photocells are set, said bladeextending in substantially parallelism with the reflected rays impingingon said photocells.
 6. In a telemeter as claimed in claim 1, the furtherimprovement wherein the convergent optical receiving system includes twomarginal fractions formed in concave mirrors the axes of which areparallel and spaced with reference to each other.
 7. In a telemeter asclaimed in claim 1, the further improvement wherein the convergentoptical receiving system includes terminal reflecting fractions of adiametrical strip cut out geometrically of a concave mirror, saidtelemeter including two pairs of photocells located adjacent spacedpoints of the axis of said concave mirror and of which one receives therays reflected by one reflecting fraction and a transparent parallelsided block inserted in the path of the rays reflected by each otherreflecting fraction to make them impinge on the other spaced point. 8.In a telemeter as claimed in claim 1, the further improvement whereinthe convergent optical receiving system includes two separate reflectingfractions adapted to reflect sepArate portions of the light issuing fromthe object, the optical axes of said fractions extending in parallelismwith a predetermined direction and wherein the separating elementincludes reflecting areas extending along the axes of the separatereflecting fractions and facing the corresponding fraction to reflectthe rays from the latter onto the corresponding photocells, the outeredges of each reflecting area extending in a plane passing between thereflecting fractions along rectilinear lines perpendicular to thedirection of the axes.
 9. In a telemeter as claimed in claim 1, thefurther improvement wherein the convergent optical receiving systemincludes two separate reflecting fractions adapted to reflect separateportions of the light issuing from the object, the optical axis of saidfractions extending in parallelism with a predetermined direction andwherein the separating element includes reflecting areas extending alongthe axes of the separate reflecting fractions and facing thecorresponding fraction to reflect the rays from the latter onto thecorresponding photocell, the outer edges of each reflecting areaextending in a plane passing between the reflecting fractions alongrectilinear lines perpendicular to the direction of the axes, the sideof each reflecting area facing away from the corresponding reflectingarea being black.
 10. In a telemeter as claimed in claim 1, the furtherimprovement wherein the convergent optical receiving system includes twoseparate reflecting fractions having different foci, adapted to reflectseparate portions of the light issuing from the object, the optical axesof said fractions extending in parallelism with a predetermineddirection, and wherein the separating elements include two coplanarreflecting areas each facing the corresponding reflecting fraction andseparated by a transparent area, the outer edges of said reflectingareas adjacent the transparent area forming rectilinear linesperpendicular to the direction of the axes of the reflecting fractionsand spaced by an amount equal to the spacing of the foci of saidfractions.